The findings were published in the medical journal Gut, the New Zealand Science Media Centre reports.

Japanese scientists discovered a labrador retriever could detect a chemical produced by cancer cells just by smelling people's breath - even in the early stages of the disease.

When smelling breath samples the dog's success rate was about 95 per cent and that figure climbed to 98 per cent when smelling stool samples.

The study's findings did not come as a surprise to Otago University's Randall Allardyce, a senior lecturer specialising in colon cancer, who said scientists were already aware of the potential for animals to detect genetic changes in other animals.

However, the latest research pointed towards a future bowel cancer screening test that could be more sensitive and specific, Dr Allardyce told NZPA.

Australian professor Graeme Young, a gastroenterologist and specialist in colon cancer, said the research raised the possibility of developing a breath test to diagnose other cancers as well.

"Dogs have an incredibly acute sense of smell and can be trained to detect these chemicals in the breath of cancer patients with a remarkable degree of accuracy," he said.

However, he questioned whether the molecules were specific to colon cancer or to a range of cancers.

"It may be, for example, that different groups of cancer with different genetic makeups give off different chemicals."

A range of tests would be needed to confirm the reliability of such a screening technique, he said.

Another bowel cancer expert, Trevor Lockett, said it was a "fascinating" study as most non-invasive tests for bowel cancer detected the later stage of the disease far more efficiently.

"But detection of early stage cancers is the real holy grail in bowel cancer diagnosis because surgery can cure up to 90 per cent of patients who present with early stage disease," he said.

Cure rates decreased dramatically as a cancer became more advanced, Dr Lockett said.

"Importantly this study tells us that there is a bowel cancer scent, that at least dogs can detect, that is not associated with other more benign bowel diseases."

However, he said there might be some similarities between the scents from different cancers which could confuse diagnosis.

"But one thing is for sure. The dogs will continue to play an important part in the future research also as scientists seek to validate any diagnostic chemical signatures that they find."

The Ministry of Health says bowel cancer is the most frequently diagnosed cancer and the second highest cause of cancer death in New Zealand.